Who are the main players in Syria's conflict?

Australia has suspended its air campaigns over Syria after a U.S. aircraft shot down a Syrian military jet, prompting the Russian military's suspension of incident prevention channels and an announcement that airborne objects would be tracked west of the Euphrates, local media cited the Australian Defense Department as saying Tuesday.

In Canberra, a Defense Department statement said on Tuesday that "Australian Defense Force protection is regularly reviewed in response to a range of potential threats".

Gayle Tzemach Lemmon, a senior fellow at the Council on Foreign Relations, said Monday that the downing of the Syrian jet, together with Iran firing missiles into Syria over the weekend, marked "a dramatic escalation in a war the United States had not meant to fight".

The top USA military officer says Washington is working to re-establish communications aimed at avoiding mishaps involving US and Russian air operations in Syria.

-Russian military "deconfliction" hotline in response to a US shootdown Sunday of a Syrian fighter jet.

In another first, Iran - another close Assad ally - fired ballistic missiles at IS targets in eastern Syria, in the province of Deir el-Zour, later on Sunday.

The Syrian army said the "flagrant attack" would have "dangerous repercussions".

What the recent incidents "indicate is a complicated and complex battlespace, and we continue to try to operate transparently and to communicate intentions around our actions so it is clear we are focusing on the defeat of ISIS in Syria", US Central Command spokesman Colonel John Thomas said on Monday. The Syrian jet was destroyed by the attack. The muscle-flexing comes amid the worsening of a long-running feud between Shiite powerhouse Iran and Saudi Arabia, with supports Syrian rebels and has led recent efforts to isolate the Gulf nation of Qatar. "It seems that the US under Donald Trump is the source of danger for the Middle East and the whole world on a qualitatively new level". The agreement covers four zones in Syria where the rebels are fighting pro-government forces.

US -backed opposition fighters said Assad's forces have been attacking them in the northern province of Raqqa and warned that if such attacks continue, the fighters will take action.

Officials emphasize the strikes were all conducted in self-defense after pro-regime forces ignored warnings. SDF fighters are aligned with the Americans in the campaign against the Islamic State group.

The push by the Syrian government forces in the Daraa area appears headed for the Jordanian border, two weeks after Assad's troops reached the border with Iraq for the first time in years. He said government forces began attacking SDF on Saturday, using warplanes, artillery and tanks in areas that SDF had liberated from IS.

The Britain-based Syrian Observatory for Human Rights says it was extended 24 hours.